Technical ABS sensor multimeter testing

[syoung]

Hi everyone, New to posting on the forum but have used it quite a bit for help in the past so thank you!!
I have a 2008 punto grande that has seen better days. Latest of which is an ABS light on. I know the best thing to do is to get the codes read but i'm really just trying to get this problem fixed so I can get the car MOT and sold so don't want to invest too much into it.
I have done lots of looking online and understand that you can check the wheel sensors with a multimeter by reading the resistance across the two terminals. I have tried this on both front sensors and one rear sensor and have had no luck getting any readings for either resistance or for voltage while spinning the wheel by hand.
Does anyone have any advice?

Thanks

 

[chris3234]

You can't test a abs sensor with a multimeter as fast as I know you'd need an oscilloscope to test the pulse's

 

[portland_bill]

You'd need an oscilloscope to test output pulses, but a simple multimeter can test the resistance. Might be difficult to find the expected resistance value, but all should be similar. Any with a high or low resistance is suspect.

Brother's Mk1 Discovery showed a wheel sensor fault, and the workshop manual gave a resistance figure of 950ohms. No idea whether this is typical, but it may help determine the multimeter range.

 

[Bernievarian]

There are two kinds of wheel speed sensor: active or passive. Because they can hardly work at low speed, the passive sensors are nowadays less used. They were testable with multi(ohm)meter for internal coil continuity/ground shortage and their signal (speed dependent AC voltage) was also multimeter measurable.
The active sensor contains electronics and needs to be power fed, its signal is PWM type and can't be measured with a multimeter, you'd need an o'scope to check it.

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

 

[syoung]

There are two kinds of wheel speed sensor: active or passive. Because they can hardly work at low speed, the passive sensors are nowadays less used. They were testable with multi(ohm)meter for internal coil continuity/ground shortage and their signal (speed dependent AC voltage) was also multimeter measurable.
The active sensor contains electronics and needs to be power fed, its signal is PWM type and can't be measured with a multimeter, you'd need an o'scope to check it.

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

THANK YOU!!
I guess the 08 punto is in fact using the active sensors. lol.
Makes a lot more sense now as none of the sensors were giving me any kind of resistance reading at all.

 

[kjeldio]

Yes, it's using a Hall-effect sensor, I think it's possible to use a much cheaper logic probe to test it. (Go / no go test, don't need to be exact), error will probably be due to a broken wire. (wires are bent every time you turn the steering wheel or drive over a bump on the road.)
BRs. Kjeld